Direct solid-phase synthesis and fluorescence labeling of large, monodisperse mannosylated dendrons in a peptide synthesizer

Fluorophore-labeled glycodendrimers have potential use in the study of carbohydrate-protein interactions by fluorescence spectroscopy and imaging methods. The current solution-phase methods for preparation of such glycoconjugates are labour intensive. On the other hand, the intrinsically more efficient solid-phase methods have been explored only at low generations. Herein we disclose a direct, expedient glycodendrimer synthesis from commercially available or easily prepared building blocks by machine-assisted solid-phase peptide synthesis (SPPS). Large, monodisperse 4th- and 5th-generation polylysine dendrons are prepared and capped with 16 and 32 mannose residues, respectively, in a single synthetic operation. Incorporation of a C-terminal lysine residue in the 4th-generation dendron allows fluorescence labelling with a number of common labels on resin, in organic solvent or in aqueous buffer, as required. A single HPLC purification is sufficient in all cases to obtain a homogeneous sample. The monodispersity of the glycodendrons is confirmed by MALDI-TOF. FITC-labeled 4th-generation glycodendron is an excellent probe for the imaging studies of mannose-receptor-mediated entry of into dendritic cells by confocal fluorescence microscopy.